High intensity light sources, and particularly white high intensity light sources, are interesting for various applications including spots, stage-lighting, automotive lighting and digital light projection. For such purposes, as well as for obtaining a desired light shape, light distribution and color distribution with a point of high intensity, it is possible to make use of so-called light concentrators where short wavelength light is converted to longer wavelengths in a highly transparent luminescent material. Such a transparent luminescent material is illuminated by LEDs to produce longer wavelengths within the luminescent material. Converted light, which will be waveguided in the luminescent material, is extracted from a surface leading to a point of high brightness.
Document WO 2012/056382 A1 describes in one embodiment a lighting device comprising a waveguide and a light source. The waveguide may be provided with a luminescent material arranged on or in the waveguide and may thereby be configured to convert light from a light source into luminescent material emission.
A problem associated with this configuration is related to bringing enough light to the light guide while keeping the temperature relatively low. In the prior art configurations LEDs, and in some configurations densely packed LEDS, e.g. 30, 40 or even 50 LEDs, are placed at a close distance from the light guide in order to couple in as much light as possible. As a result of the LEDs being too close to the light guide heat from the LEDs leads to heating of the light guide and decreases the optical performance of both the light guide and LEDs.
DE102008012316A1 discloses a semiconductor light source and a luminescent converter element both arranged on a common heat sink. Light emitted by the semiconductor light source is guided via a light guide to the luminescent convertor element.
EP2202444A1 discloses a LED module that emits light towards a phosphor module. The phosphor module includes a transparent layer, closest to the LED module, and a phosphor layer directly adjacent to the transparent layer. The phosphor module may further include a heat sink.
WO2012/006128A2 discloses a high lumen output and brightness illumination module using an excitation light source and wavelength conversion part with multi-channel heat dissipation.